Do psychotic symptoms predict future psychotic disorders in adolescent psychiatry inpatients? A 17-year cohort study

Background: Individuals with a psychiatric inpatient admission in adolescence have a high risk of schizophrenia-spectrum disorders (SSDs) when followed to adulthood. Whether psychotic symptoms predict subsequent SSDs in inpatient cohorts, however, is an important unanswered question.

Methods: The sample consisted of adolescents (aged 13-17) admitted to psychiatric inpatient care (Oulu, Finland) from April 2001 to March 2006. Psychotic symptoms were assessed with the Schedule for Affective Disorders and Schizophrenia. Specialized health care use and diagnoses were followed up in national health care registers until June 2023. Cox regression was used to predict SSDs by the presence of baseline psychotic symptoms.

Results: Of 404 adolescent inpatients admitted with non-psychotic mental disorders, 28% (n = 113) reported psychotic symptoms: 17% (n = 68) subthreshold and 11% (n = 45) full threshold. By the end of follow-up, 23% of the total cohort went on to be diagnosed with an SSD. Subthreshold psychotic symptoms did not differentiate patients who would subsequently develop SSDs (cumulative incidence 24%; HR = 1.42, 95%CI = 0.81-2.50). Full-threshold psychotic symptoms, on the other hand, were associated with an increased risk of subsequent SSDs (cumulative incidence 33%; HR = 2.00, 95%CI = 1.12-3.56). Most subsequent SSDs (83%), however, occurred in individuals who had not reported threshold psychotic symptoms during inpatient admission.

Conclusions: There was a high risk of subsequent SSDs among adolescent psychiatry inpatients when followed over time. SSDs were not predicted by subthreshold psychotic symptoms. Full-threshold psychotic symptoms were associated with an increased risk of subsequent SSDs, though with low sensitivity.